On trans-oceanic flights, it is often desirable to fly an aircraft through a narrow air current corridor where the aircraft can operate at peak performance. As a result, significant amounts of time and fuel can be saved, especially on extended flights. Since these corridors have been observed to remain relatively unchanged in location for several hours, it is often desirable to navigate several aircraft through the corridor at a given time. In fact, economically, it is preferable to navigate as many aircraft through these corridors as possible.
The current ATC system uses ground-based surveillance radar beacons and airborne transponders to track aircraft over land areas. However, since the surveillance radar does not extend across the ocean, the location of an aircraft on a trans-oceanic flight is not precisely known at all times. Consequently, in order to assure safe operation, aircraft have had to maintain great separation distances. With this uncertainty of location and the concomitant need for great separation distance, it has been difficult to take full advantage of these corridors.
With the advent of TCAS, many trans-oceanic aircraft are expected to be equipped with on-board surveillance as part of the TCAS equipment. However, with a typical TCAS, the flight crew on the TCAS protected aircraft will not be provided with all the desirable information regarding the aircraft surrounding them. Furthermore, the information that is provided is constantly changing and is often difficult to detect and interpret. For example, traffic information is typically provided to the flight crew by a display device showing the protected aircraft at the center of the display and the surrounding aircraft are shown in a full 360.degree. circle around the protected aircraft. With such a display, a maneuver of the protected aircraft will cause all the representations of surrounding aircraft to be relocated on the display. This makes it difficult to keep track of any particular aircraft, especially when several maneuvers are made in a short time.
Similarly, when a busy airport comes under IFR conditions it often results in increased delays and take-offs and landings in order to comply with the increased separation requirements. If more aircraft could be safely guided through the narrow corridors on approach and take-off then the delays could be greatly reduced.
Consequently, there exists a need to utilize the TCAS system to provide an overall ATC system which is able to more safely exploit the benefits of navigating through narrow corridors by an enhancement of that TCAS system so it is more capable of easier communication and utilization of unique aircraft identification information.